GTL File

What are GTL files and how to open them

Are you having problems opening a GTL file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your GTL files.

What is a GTL file?

A .GTL file is a Gerber Top Layer file.

A Gerber Top Layer File (.GTL) carries the artwork for the top copper layer of a printed circuit board (PCB), showing where copper should remain or be etched away on the component side. It is generated by PCB design tools when preparing manufacturing output, and serves as one of several layer files that together define all copper, silkscreen, solder mask, and drill data.

Inside the .GTL file, the content follows the Gerber specification (RS-274X and newer revisions) and typically includes vector graphic primitives (lines, flashes, fills, apertures) that outline pads, traces, pours, and other copper features. The file names and extensions like ".gtl" are naming conventions (popularized by tools such as Altium, Protel, etc.) rather than required by the specification; the actual purpose of each file is more reliably conveyed by internal attributes (for example, .FileFunction,Copper,L1,Top*) in the Gerber header.

A .GTL file begins with standard Gerber header attributes. One key attribute is .FileFunction, which for the top copper layer must be "Copper,L1,Top[,type]" - here L1 is layer number one (the physical top copper layer), "Top" indicates side, and an optional type field may further describe the layer's nature (such as Signal or Mixed). These formal identifiers help CAM, assembly, and fabrication tools place the layer correctly.

How to open GTL files

We have identified one GTL opener that is compatible with this specific type of GTL file.

Programs that open Gerber Top Layer files

Last updated: August 6, 2026

Various apps that use files with this extension

These apps are known to open certain types of GTL files. Remember, different programs may use GTL files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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